Biochemical MR of cartilage and disc in the temporo-mandibular joint

Temporomandibular disorders (TMD) are among the most common disorders in the field of oro-maxillofacial medicine. Patients describe pain and clicking phenomena as cardinal symptoms with prevalence ranging from 20% to 85%. Clinical experience has shown that such symptoms will not disappear spontaneously and should therefore be treated by appropriate therapy. In these patients accurate diagnostic evaluation and assessment is of particular importance. In addition to history and clinical status of the temporomandibular joint (TMJ) imaging modalities are needed to provide a composite of findings on which treatment planning can be based. In this project multiparametric MR will be performed to assess the different MR parameters of disc and cartilage of the TMJ both in vitro and in vivo at 3 and 7T. For clinical application of compositional (biochemical) MR techniques high-field (3 Tesla) and ultrahigh field (7 Tesla) MR scanner with dedicated temporomandibular joint (TMJ) coils with modern technology (multi-element coil) will be necessary. The higher signal to noise ratio provided by high field and ultra high field MR scanner and modern coil technology will also provide high resolution morphological imaging which is necessary for the visualization of the thin cartilage layers in the TMJ and enough signal for MR techniques such as sodium imaging. Biochemical MR methods such as dGEMRIC, T2 and T2* mapping and diffusion-weighted imaging will be adapted for the temporomandibular disc and cartilage and sodium imaging and ultrashort-TE technique (UTE) will be implemented for the first time in the clinical evaluation of the TMJ. These new techniques will be validated with histological comparison derived from human TMJ specimen studies. In a further step high resolution morphological and biochemical protocols optimized in volunteers will be used to quantitatively evaluate disc and cartilage in the TMJ in two different groups of patients compared to healthy age-and gender-matched volunteers. The application of multi-parametric, biochemical MR techniques will help to visualize biochemical and biomechanical properties of the disc in the normal and pathological state and will help to monitor different therapies of the temporomandibular joint over time. We expect that compositional (biochemical) MR is more sensitive than morphological MR for the detection of disc and cartilage disease in the TMJ and may allow quantitative monitoring of different therapies in patients with temporomandibular joint disorders.

In the course of this project the MRI depiction was improved regarding the morphology and pathology of the highly complex temporomandibular joints. Biochemical MRI techniques were applied to the articular disc (a fibrouscartilage within the joint) for the first time. Joint pathologies are considered one of the most common causes of illness among the adult population. Temporomandibular disorders are characterized by pain and clicking phenomena, often also restrictions of motion, parafunctions, headache and tinnitus. As morphological substrate in the joint, disc displacement and/or degenerative mutations of the articular cartilage might be the cause.T2 mapping allows for an evaluation of these degenerative processes, dGEMRIC with the application of a contrast agent shows the loss of glycosaminoglycan in the earliest stage of cartilage degeneration.Subsequently, the optimized MRI protocols were expanded to patient studies. One of the focal points was to use dGEMRIC for early detection of degenerative mutations in patients suffering from pain in the temporomandibular joint region, where conventional MR tests could not detect a pathology. Another focal point was the use of T2 mapping with patients suffering from various disc malalignments (disc dislocations) in connection with pains in that region.The fibrocartilaginous tissue of the articular disc is of significant biomechanical relevance. Through a study with anatomical specimens (human cadavers), the biochemical MR protocol was evaluated in direct comparison with a histological analysis of the collagen fiber network. The aim was to determine and quantify the collagen fiber network and thus the orientation of collagen fibers within the disc in a first systematic analysis of collagen fiber orientation in human discs. This study can be the basis for further research supporting the connection between collagen fiber arrangement and MRI results.The application of MRI testing in temporomandibular joint diagnosis has proven itself in practice. Details of the disc morphology can be displayed in MRI and diagnosed. Elevated magnetic field strength in the examination of joints can lead to enhanced detail rendition at equal evaluation periods.Through the application of biomorphological procedures it could be demonstrated that pressures may lead to degenerative changes in the cartilage. Through early detection of biochemical changes arthritic developments could be detected and treated at an early stage.